That may explain why the recent arrival of La Niña—a global weather pattern that in the past has led to greater-than-average rainfall in Australia—is bringing little relief this spring.

La Niña's unfulfilled promise of rain has hit the Murray-Darling River Basin in southeastern Australia especially hard. The area, roughly the size of France and Spain combined, is Australia's food bowl, with about 41 percent of the country's agricultural activities taking place there.

Tens of thousands of farms in three Australian states depend on the River Murray, which no longer carries enough water to flow to the ocean. By the end of the most recent winter, river flows and reservoir levels in some parts of the country were at all-time lows.

Even if La Niña does persist and bring heavy rainfalls, it will take several seasons for the catchments to fill up again.

Without water, some of the local farms have had at least two seasons of crop failure. Farm debt was $412,000 Australian, up from $150,000 in 1990, according to the National Australia Bank.

The South Australia Farm Federation said recently that crop failures could force 20 percent of the state's farmers off the land in the next year.

That's already hitting consumers in the wallet. Food prices are beginning to inch upward, and record high prices for grain are hitting the cattle industry, which has said consumers should brace for much higher beef prices.

The Australian government has spent 1.9 billion dollars in the last few years in what it calls "exceptional circumstances" payments to lend a hand to farmers still trying to till the soil. It also recently doubled an offer, to $150,000, to any farmer who decides to leave his or her land.

La Niña and El Niño

Australia is heavily influenced by weather patterns in the Pacific. Generally, Australia goes dry during El Niño cycles, a warming in the tropical Pacific that has worldwide consequences. La Niña, the opposite effect, tends to bring heavier-than-normal rainfall.

But the current La Niña phase has failed to deliver anything but patchy rainfall in Australia.

"Although we have some sort of La Niña out there, the sea-surface temperatures around the Australian coast have not warmed up yet," said Roger Stone, professor of climatology and water resources at the University of Southern Queensland in Toowoomba.

Many farmers had banked on the fact that La Niña was going to bring rain to reservoirs, dams, and other catchments that are basically dry.

"Also, interestingly, La Niñas over the past 30 years are not delivering rain like they used to in many regions," he said.

In fact, neither El Niño nor La Niña has had a predictable influence on Australian weather recently.

"El Niños have also been behaving strangely," noted Andy Pitman, director of the Climate Change Research Center at the University of New South Wales in Sydney. "There have been quite sustained patterns and we don't know why."

This drought has extended over both weather patterns, which is unusual, he added.

Ocean temperatures in the Indian Ocean also play a major role in Australia's rainfall patterns. These waters have been colder than normal in the past few months, exacerbating the problem, experts say.

Global Warming Issue

Droughts are normal and natural in Australia. A growing number of scientists, however, believe the severity of Australia's Big Dry can be blamed on global warming.

"Droughts are natural," Pitman said. "But the level of drought is worse now because of higher temperatures that are driving increased evaporation. At the moment we can't explain the higher temperatures except by global warming."

Neville Nicholls, professor of geography and environmental science at Monash University in Clayton, Victoria, added that the southern fringe of Australia has been getting drier, which also may be linked to global warming.

"Our climate models all suggest that this is the response you should get from increased greenhouse gases, so there is a developing consensus amongst climate scientists that human activities are partly responsible for this long-term rainfall decline," he said, adding that they expect this to continue.

What is happening in Australia, Pitman said, should be a cautionary tale to the rest of the world that it's important to prepare now for more severe drought.

"In some regions, as happened in Australia, global warming will lead to abrupt regional change," he said. "In Australia, it arrived. In other regions, too, the changes will be rapid and sudden and confronting."